Lateral semiconductor components having a drift path running in the lateral direction of the semiconductor body and having a current path thus running in the lateral direction are generally known. Such components may be formed both as bipolar components, such as diodes or IGBTs, for example, or as unipolar components, such as MOSFETs or Schottky diodes, for example.
In the case of diodes, the two terminal zones are doped complementarily and the drift zone or base zone is doped by the same conduction type as one of the terminal zones, but more weakly. The two complementarily doped terminal zones form the anode and cathode zones of the diode.
In the case of a MOS transistor, a first terminal zone serving as source zone and of the same conduction type as the second terminal zone serving as drain zone is present, the source zone being separated from the drift zone by means of a body zone of the second conduction type. A gate electrode formed in a manner insulated from the semiconductor zones serves for forming a conducting channel in the body zone between the source zone and the drift zone. The source zone and the drain zone are of the same conduction type in the case of a MOSFET, while the source zone, or emitter zone, and the drain zone, or collector zone, are doped complementarily in the case of an IGBT.
What is crucial for the dielectric strength of such components, that is to say for the maximum voltage that can be applied between their terminal zones before a voltage breakdown occurs, is the configuration, here in particular the doping and dimensioning in the lateral direction, of the drift zone. The drift zone takes up the majority of the applied voltage in the case of such components in the blocking state, that is to say in the case of a diode when a voltage is applied which reverse-biases the pn junction between the anode and the drift zone, and in the case of a MOS transistor when a load path voltage is applied and the gate electrode is not driven. A reduction of the dopant concentration of the drift zone or a lengthening of the drift zone in the current flow direction increases the dielectric strength, but is detrimental to the on resistance.
In accordance with the compensation principle, in order to reduce the on resistivity of such lateral components, it is known from DE 199 58 151 A1 or DE 198 40 032 C1 to provide a compensation structure with complementarily doped zones arranged adjacent in the drift zone, which are mutually depleted of charge carriers in the off-state case. This results in the possibility of doping the drift zone more highly with the dielectric strength remaining the same, as a result of which the on resistance decreases.
These complementarily doped zones that in each case extend in elongated fashion in the lateral direction of the semiconductor body between the terminal zones may be fabricated for example by successive deposition of respectively complementarily doped epitaxial layers. Such a construction principle is cost-intensive, however, since a plurality of epitaxy steps and one to two masked dopant implantations per epitaxial layer are required.
In the case of vertical semiconductor components, for the purpose of reducing the on resistance, it is additionally known to provide at least one field electrode running in the vertical direction of the semiconductor body in a manner insulated from the drift zone, said field electrode being at a defined potential. In the off-state case, said field electrode likewise compensates for charge carriers in the drift zone, which results in the possibility of doping the drift zone of the component more highly compared with components without such a field electrode, with the dielectric strength remaining the same, which in turn leads to a reduction of the on resistance.
U.S. Pat. No. 4,941,026 describes such a vertical component with a field electrode that is at a fixed potential. Semiconductor components with a field electrode arranged in the drift zone are described, moreover, in U.S. Pat. No. 6,717,230 B2 or U.S. Pat. No. 6,555,873 B2.